Serialize VAT collection mutations with payment operations (#326)

## Summary

- Makes Stripe Terminal card payment intents always use 25% moms in the
API, independent of any client-supplied `tax_percentage`.
- Updates amount calculation, metadata persistence, stored-intent reuse
matching, the authoritative OpenAPI contracts, and operation-specific
Writerside outputs.
- Prevents double charging and false order closure across stale,
concurrently succeeded, partially recorded, or mismatched intents.
- Serializes payment create/capture/closure with order-item changes and
every order-to-invoice-collection reassignment through shared database
locks.
- Converts expected lock contention and reconciliation cases into
deliberate 409 responses.

## Exact-head evidence

Current head: `3a0f70d315a94d2efe586a2188d2c54f8ff11cd4`

- PHP syntax passed for all changed runtime files.
- Focused Orders suite: **42 tests / 293 assertions passed**.
- `git diff --check` passed.
- Fresh exact-head Tests and Qodana are running.
- Every Codex finding has a concrete reply; a fresh exact-head review is
requested below.

## Safety behavior

- Caller-controlled VAT is absent from request contracts; fixed 25% moms
is server-owned.
- A succeeded payment is preserved, requires the full expected
`amount_received`, and cannot close a changed/mismatched or
already-claimed collection.
- A compatible partially recorded Stripe closure is completed
idempotently; conflicting partial state fails closed for manual
reconciliation.
- Every cancellation/delete caller honors a concurrent-success result
and never falsely reports a completed payment as cleared.
- Price changes and invoice-collection reassignment share the payment
lock through validation, capture, post-capture reload, and closure.
- Reader changes are persisted only for reusable matching intents, so
stale intent cancellation targets the original terminal.
- Accepted legacy succeeded intents normalize stored tax to 25% before
response construction.

---------

Co-authored-by: Jeppe Bundgaard <jb@truckwash.dk>

documentation/generated/openapi.json

@@ -9856,6 +9856,7 @@
           "Orders"
         ],
         "summary": "Create Stripe payment intent",
+        "description": "Creates a Stripe Terminal card payment intent with fixed 25% moms.",
         "operationId": "createStripePaymentIntent",
         "requestBody": {
           "required": true,
@@ -9873,9 +9874,6 @@
                   },
                   "reader": {
                     "type": "string"
-                  },
-                  "tax_percentage": {
-                    "type": "integer"
                   }
                 }
               }

documentation/topics/generated/createStripePaymentIntent.topic

@@ -12,7 +12,7 @@
     </chapter>
     <chapter title="Operation" id="operation">
         <p>Operation ID: <code>createStripePaymentIntent</code></p>
-        <p>Create Stripe payment intent</p>
+        <p>Creates a Stripe Terminal card payment intent with fixed 25% moms.</p>
     </chapter>
     <chapter title="Authentication" id="authentication">
         <p>Security requirements:</p>
@@ -32,9 +32,6 @@
     },
     &quot;reader&quot;: {
       &quot;type&quot;: &quot;string&quot;
-    },
-    &quot;tax_percentage&quot;: {
-      &quot;type&quot;: &quot;integer&quot;
     }
   },
   &quot;required&quot;: [